Heater for burning liquid fuel,primarily benzine,especially extraneous heater for motor vehicles



United States Patent Inventors Appl. No.

Filed Patented Assignee Priority Eugen Stump Stuttgart-Unterturckheim; (-erhard-Juergen Frankle, Grunbach, Germany 743,065 7 July 8, 1968 Dec. 1, 1970 Suddeutsche Kuhlerfabrik Julius Fr. Behr Stuttgart-Feuerbach, Germany July 7, 1967 Germany HEATER FOR BURNING LIQUID FUEL,

PRIMARILY BENZINE, ESPECIALLY EXTRANEOUS HEATER FOR MOTOR VEHICLES 15 Claims, 3 Drawing Figs.

U.S. Cl......

[5| 1 int; Cl F24h 3/02 [50] Field of Search l26/l l0, ll0(B), l l6, ll6(A); 237/l2.3(l)

[56] References Cited UNITED STATES PATENTS 2,645,278 7/1953 Holthouse, Sr., et al l26/l lOX 2,757,662 8/l956 Baier et al l26/l 10B FOREIGN PATENTS 785.288 l0/l957 Great Britain l26/l 16A Priman ExaniinerCharles J. Myhre Attorney-Robert H. Jacob ABSTRACT: Heating device primarily for motor vehicles operated with liquid fuel having a burner, a flame cylinder. and a heat exchanger with a chamber arranged ahead of the pressure fuel nozzle into which extends the electrode of a spark plug and air means are provided for supplying a partial quantity of the air of combustion into the chamber.

HEATER FOR BURNING LllQUlD FUEL, PRIMARILY BENZINE, ESPECIALLY EXTRANEOUS HEATER FOR MOTOR VEHICLES BACKGROUND OF THE INVENTION The invention relates to extraneousheaters for motor vehicles of the hydrocarbon burning type. More in particular, the invention concerns a heater burning liquid fuel, particularly an extraneous heater for motor vehicles, comprising a burner, a flame chimney and a heat exchanger.

Heaters of this type are primarily used for heating motor vehicles and in given cases also for preheating motor engines. This requires on the one hand, small compact structural volume and on the other hand, high heating efficiency. in known air heaters the heating air flows about the burning chamber, while the burning chamber constitutes the heat exchanger for the fluid to be heated which circulates about this heating chamber. Thus the wall of the burner chamber is simultaneously the wall of the heat exchanger around the outside of which flows cold'fluid. This results in the problem that the flame from the burner comes in contact with a cold burning chamber wall and that results, as is well known, in decreased fuel burning efficiency and deposits of soot on the wall of the burner chamber.

The desired small outer dimensions of the heater make it necessary to obtain as large a flame length as possible to insure of efficient combustion. in this state, however, the flame must not come into contact with cold wall portions, because this would result in incomplete combustion. Heating devices of this type known heretofore are also not satisfactory as far as the ignition conditions are concerned This is essentially due to the type of fuel mixture used, and especially with benzine and similar fuels, due to the difficulty of meeting the requirements of stoickiometric principles.

The extraneous heating devices in question are to be operated in a temperature range from 40 C to l C. However, the varying air temperature results in the supply of different volumes of air depending on the temperature, while the speed of the blower remains the same. This also changes the mixture proportions between atomized fuel and air of combustion. Furthermore, ignition of the mixture takes place only within definite relativelynarrow mixture proportions. Also, the variable potential of the source of current causes ignition difficulties, because the speed of the blower motor fluctuates and thus supplies different quantities of air of combustion.

A heater of the type mentioned above has already been proposed where the burner chamber is defined by a first inner flame cylinder which concentrically encompasses an air nozzle, while a second, outer flame cylinder having a closed end surface concentrically surrounds the inner flame cylinder and the flame cylinders are thermally separated and insulated with respect to the heat exchanger that surrounds them.

When using benzine as fuel for a heating device there exists the danger, that as a result of the heating vapor bubbles are formed in the fuel, or that the benzine vaporizes in a manner that cannot be controlled. In order to make extraneous heating devices independent of the driving conditions of the motor vehicle, high pressure must be available from the combustion air blower. This requires a correspondingly large diameter.

SUMMARY 0; THE lNVENTlON It is, therefore, an object of the invention to create a heating device operated with liquid fuel, particularly benzine, which meets the operating requirements better than the heating devices known or proposed heretofore and which independently of the prevailing outside temperature and of the available potential insures reliable ignition, avoids vaporization of the fuel and which with a small structural volume provides great heating efficiency.

in accordance with the invention this problem is solved in that a chamber is arranged in the direction of flow behind a fuei atomizing nozzle, into which extends the electrode of a spark plug and where means are provided in this chamber for the supply of a partial amount of the air of combustion. By this means it is accomplished that a partial air current of the quantity of air of combustion is introduced into the cone of fuel that is produced by the atomizing nozzle. in this manner mixture of the partial amount of air with a part of the atomized fuel takes place locally and partially in the area of the spark plug, whereby a locally limited ignitable mixture is formed at all external temperatures and with all potential conditions.

If the blower supplies more or less air of combustion due to external temperature influence or to fluctuating potential conditions and thus a more or less voluminous partial amount of air of combustion is supplied to the chamber, then only the magnitude of the area of the ignitable mixture is changed. la the cross-sectional area of the ignition spark, however, there is always a region of ignitable mixture, so that ignition can readily take place. The air of combustion is then fed in-a known manner to this chamber.

In a particularly suitable embodiment of the invention the spark plug mounting or socket has apertures in the path of flow of the air of combustion, and a further aperture that sur rounds the spark electrode essentially in an annular manner, serves for the supply of the partial quantity of air into the chamber in front of the atomizing nozzle and for cooling the spark plug.

in order to prevent the formation of vapor bubbles in the fuel that is introduced, the invention provides furthermore a warm part for the extraneous heating device which consists of a combustion space and a heat exchanger and a cold part which contains the blower for the air of combustion with the motor for the blower and a pump for a cooling agent as well as a cooled fuel supply line to the atomizing nozzle of the burner.

By means of this subdivision in accordance with the invention it is accomplished on the one hand that the burner flame no longer comes in contact with cold parts of the burner chamber, while on the other hand the fuel supply for the burner nozzle is held to a sufficiently low temperature independently of the combustion action, in order to avoid evaporation of the fuel.

ln a particularly advantageous embodiment of the invention the fuel supply is arranged in such-a manner and the guidance of the air of combustion is so constituted that the fuel supply line is continuously in the path of flow of cold air of combustion. The cold air of combustion drawn in by the blower is thus conducted past the fuel supply line on its way to the heat exchanger and maintains it, as well as benzine flowing therein, at a sufficiently low temperature.

If in accordance with a further feature of the invention the blower for the air of combustion is provided at one side of the burner chamber and a pump for coolant on the opposite side, then the fly wheel for the blower for the air of combustion can have a larger diameter which results in a desirable decrease in noise as a result of the lower motor speed required with the same pressure. At the same time also the required driving power is decreased.

in accordance with a further development in accordance with the invention the interrupting contact points which are present in the fuel pump can be utilized for producing the sparks for the spark plug.

ln a preferred embodiment of the invention the cold part comprises a first part which contains the spark plug and the supply channel for the air of combustion, a second part containing the fuel supply line, the nozzle and the chamber for preparing the combustible mixture, a third part with the blower motor and the blower for the air of combustion, as well as a fourth part with the pump'for the cooling agent and the coolant supply.

In a preferred embodiment of the invention the heat exchanger of the heating device is in the form of an air/water heat exchanger. in this connection the heating gas channels in the heat exchanger may in accordance with a further embodiment of the invention be of U-shaped form.

Furthermore, the burner output is increased essentially in that baffle disks are arranged in the path of the air of combustion. In this arrangement the first baffle intercepts the entire air current and causes'i't to rotate, while the second baffle seizes only a partial air current.

in accordance with a further object of the invention an additional heat protection disk is provided in order to prevent undesirable heat feed back to the atomizing nozzle and to the fuel line.

The invention also concerns the electrical circuit for operating the heating device. ln accordance with the invention a protection device against overheating is provided which comprises an overheating thermostat which is arranged in the path of the flow of the fuel pump. By these means it is accomplished that in the event of overheating the device the fuel pump is turned off. Suitably the overheating thermostat is mounted on the heat exchanger casing.

A further safety device protects against blowing away the fuel. A protection relay arranged in the circuit of the motor and having contacts in the circuit of the fuel pump ascertains that in the operation ofthe fuel pump and of the ignition also the motor of the apparatus is running. Thus, if the supply cable for the motor current comes loose or falls off, no further fuel can be injected.

According to a further feature of the invention it is also possible to provide a followup switch that depends on the temperature which takes care of subsequent airing of the burning chamber after the ignition has been turned off..

Further features and advantages of the invention are illustrated in more detail schematically by embodiments of the drawings in which:

FIG. 1 is a longitudinal section of a heater according to the invention;

FIG. 2 is a portion of a longitudinal section taken along line A-A in F 1G. 1;

FIG. 3 is a circuit diagram of the safety devices according to the invention.

The embodiment as'shown in FIG. 1 has an inner flame cylinder 2 in the form of a hollow cylinder made of steel sheet metal arranged on a support plate 1. Fastened concentrically upon inner flame cylinder 2 is an outer flame cylinder 3, which is closed at its front end 4.

The heat exchanger consists of an outer casing 6, an inner casing surface 5, and U-shaped hot gas channels 7 arranged between the inner casing surface and outer flame cylinder or chimney 3. The heating fluid, generally water, is introduced through the heating medium inlet 8 and leaves through outlet 9 after being heated. The burnt gases leave the heat exchanger through the centrally located opening 10.

A blower motor ll, which drives a blower fan 12 for combustion air, is arranged in the cold portion of the device. Thereby the combustion air is drawn in through openings in the casing 13 of the motor housing, so that a portion of the combustion air flows rapidly through the winding of the motor ll, thereby simultaneously cooling it. A water pump 15 isarranged on the rearward end of the motor shaft 14. A gasket 16 seals the interior of the motor against the water pump 15. Furthermore, a spray shield 17 is provided, which serves to throw by means of centrifugal forces any moisture that may have penetrated into the chamber l8 against the outer. wall, whence it may depart through the outlet apertures. The heating fluid, preferably water, is drawn in by the pump 15 through a suction stub 19 and isfed by way ofa pressure stub 20 and a conduit 2i through the heating fluid stub 8 to the heat exchanger. A further housing part 22 is fastened by means of an anchoring bolt or the like 23 against the housing 13 of the motor ll. The housing part 22 has a spark plug socket or mounting 24 in which a spark plug 25 is seated. In a connecting member 26 which is fastened to the housing part 22 an atomizing nozzle 27 is disposed which is in communication with the fuel supply line 29 through a bore 28. A pressure pump (not illustrated) feeds the fuel along the path mentioned above to the nozzle 27. A chamber 3b is disposed ahead of the noule 27. The spark plug 25 or at least the ignition electrode 3i projects into this chamber. With the ignition turned on a spark jumps periodically from the electrode 31 to the opposite electrode 32. The spark plug mounting 2 is provided in ac cordance with the invention with apertures 33 and is so constructed that an annular space having an aperture 34 is formed around the ignition electrode. A heat protecting shield 35 preferably disposed between the chamber 30 and the atomizing nozzle 2'7. The fuel atomized by the a'tomizing nozzle I27 forms a fuel cone 36 which extends through the chamber 30 into the ignition area 37. Generally ring shaped baffle plates 38 having obliquely disposed guide blades 39 take care of intimate mixing of the air of combustion with the atomized fuel which is drawn in and supplied by the combustion air blower A part of the air of combustion supplied flows through the aperture 33 into the interior of the spark plug mounting 2d and from there through the aperture 34 into the chamber 39. An area is formed around the ignition electrode 3! in which the partial air quantity supplied mixes locally and partially with atomized fuel. Thus, a locally limited mixture ready to be ignited is provided under all temperature and potential conditions. I

The combustion air which is forced in flows on the one hand partly to the spark plug and cools the same, while another part flows around the attachment 26 with the bore 2% for the fuel supply and therefore always keeps the fuel at a suitably low temperature thereby avoiding evaporation or bubble formation. The burner flame extends then into the inner flame cylinder while the gases of combustion are then diverted at the closed part 4 and flow about the outer flame cylinder 3. From the gases of combustion conducted through the U-shaped parts or channels 7 the heat exchange with the heating fluid takes'place'which flows in the space between the outer casing 'and the inner casing 5. The heat carrier agent supplied by the pump 15 is preferably heated in the counter current by the gases of combustion and is available for further use at the outlet stub 9. As shown in thecircuit diagram according to H6. 3, the main current circuit is provided with a fuse 41. The device can be turned on manually by means of a switch 42. However, it is also possible to construct the switch 42 as a contact of a time switch relay 43. By means of the time switch relay a desired time can be set when the device ignites auto matically and heats the motor vehicle so that the user can find the vehicle ready for operation and heated at the set time without waiting during a preheating period. If desired, a main switch 44 can be provided when the relay 43 is used. The switch or the contact 42 closes the circuit to the motor ll. Parallel thereto a control lamp 45 may be placed in the circuit. A temperature controlled followup switch 46 may be arranged in the motor current circuit which provides that after turning off the heat the blower continues to run and thus the heating device is cooled accordingly. Furthermore, the switch or contact 42 closes the circuit to the fuel pump 47 as well as to an ignition coil 48. The ignition is effected by way ofa condenser 4-9, while a contact 50 of the fuel pump acts simultaneously as an ignition interrupter. A safety thermostat is located in the circuit to the fuel pump and to the ignition circuit. The sensing device of the thermostat is suitably arranged at the housing of the heat exchanger.

Furthermore, a control thermostat 52 may be provided which has a sensing device in the circuit of the heating fluid so that a predetermined selectable heating fluid temperature will be maintained.

The device is turned on by means of the switch 42 or by the time switch relay 43 as a result of which the continuous ignition, the fuel pump and the motor are started. Simultaneously the control lamp 45 lights up as the followup switch as is heated, its contacts close, whereby as the switch 4 or 42 is opened subsequent airing of the burner chamber takes place. Only when the subsequent heating is terminated, also the con trol lamp is extinguished. The overheat thermostat 55. turns off the fuelpurnp 47 and the ignition in the event of excess temperature. This thermostat must be set back manually after it has responded.

In order to insure that during operation of the fuel pump and the ignition also the motor 11 is running, a protective relay 53 is provided in the motor lid. If the protective relay is devoid of current for anyreason, then the contact 54 opens so that no further fuel can be injected. In the event of a short circuit in the motor lid or in the motor, the fuse 41 responds. The invention is not limited to the embodiment illustrated and described. It is also readily possible to provide an air/air-heat exchanger in lieu of the air-water heat exchanger illustrated. What is essential is that by conducting the air of combustion independently of the quantity of combustion air supplied, there is always an ignitable mixture available in the cross-sectional area of the fuel cone at the level of the ignition spark so that ignition may take place under any circumstances. For example, the spark plug mounting 24 may have a further aperture 55 in the path of flow of the air of combustion so that the part of the air of combustion supplied to the chamber 30 can be controlled as desired.

Having now described our invention with reference to the embodiments illustrated in the drawings what we desire to protect by letters patent is set forth in the'appended claims.

We claim: s

1. Heating device burning liquid fuel, especially benzine, for useprimarily in motor vehicles, comprising a heat exchanger, a flame cylinder in said heat exchanger and a burner disposed proximate one end of said flame cylinder,-said burner having a fuel atomizing nozzle and a burner chamber extending from said nozzle toward said flame cylinder, means for supplying liquid fuel to said nozzle and means for supplying a part of the air of combustion into said burner chamber, a spark plug mounting proximate said burner chamber and a spark plug in said mounting having an electrode extending into said burner chamber at least with the igniting end thereof, and means for supplying the remainder of the air of combustion downstream of said burner chamber.

2. Heating device in accordance with claim 1, comprising apertures in said spark plug mounting defining passages for air of combustion and a generally annular aperture defined by said mounting around said electrode.

3. Heating device in accordance with claim 1, said device being subdivided into a warm part comprising said burner chamber and said heat exchanger, and a cold part including a pump for air of combustion and a pump for heating fluid, and

a fan motor for said pumps, and an air cooled fuel supply line for feeding fuel to said fuel nozzle.

4. Heating device in accordance with claim 3 comprising a housing portion around said fuel supply line and said burner nozzle defining an air space for cold air of combustion.

5. Heating device in accordance with claim 4 where said fan motor is in said cold part having a blower defining said pump for air of combustion at one end proximate said burner nozzle and having said pump for heating fluid at the other end.

6. Heating device in accordance with claim 5 where said cold part further includes a portiontcontaining said spark plug and defining a channel for air of combustion, a portion containing said fuel supply line and said burner nozzle, :1 portion encompassing said motor and said blower, and a portion containing said pump for heating fluid.

7. Heating device in accordance with claim 6 where said heat exchanger is an air-water heat exchanger.

8. Heating device in accordance with claim 1, comprising baffles in the path of combustion air and fuel mixture proximate said burner chamber intermediate said spark plug and said flame cylinder.

' 9. Heating device in accordance with claim 1 including U shaped channel members extending generally longitudinally through said heat exchanger.

10. Heating device in accordance with claim 8 where a heat shielding plate is disposed intermediate said burner nozzle and said burner chamber.

11. Heating device in accordance with claim 1, comprising a fuel pump connected to said fuel supply line and an ignition coil for said spark plug, said fuel pump having a contact servingas an ignition interrupter.

. 2. Heating device in accordance with claim 11, including an overheating protection device comprising an overheat responsive thermostat, a power supply circuit in which the pump motor of said fuel pump is connected, and said protection device being connected in said circuit with the fuel pump motor.

13. Heating device in accordance with claim 12, including a protection relay in the circuit of said fan motor and a contact in the circuit of said pump motor responsive to the operation of said relay to stop the pump when said relay is devoid ofcurrent.

14. Heating device in accordance withclaim 13, including a 

